With the increasing interest in distribution automation, distribution power flow is important for applications like VAR planning, switching, state estimation and especially optimization. Typically, a distribution system originates at a substation and continues to a lower voltage for delivery to the customers. There are several tools for transmission system analysis. These tools include Newton Raphson, Gauss Seidel and fast decoupled techniques. These techniques however sometimes fail to converge when applied to distribution systems due to their higher resistance/reactance (R/X) ratio of the lines, making them ill conditioned. Distribution systems typically have a radial topological structure where the loads are not always constant power. With the increase in distributed generation (DG) there is a critical need to develop analysis tools to study the effect they will have on the distribution systems. Also, shipboard power systems are different from terrestrial distribution systems, as they are tightly coupled and have multiple generators. This dissertation focuses on developing a software program to perform the power flow analysis of terrestrial as well as shipboard power systems. Components are modeled considering the mutual coupling of cables and the tightly coupled nature of the ship systems. The algorithm is built and tested on I test cases. The distributed generator is modeled as both a PQ (constant power factor) and a PV (constant voltage) node. This dissertation also focuses on reconfiguration for restoration of unbalanced distribution systems. Reconfiguration is changing the status (OFF/ON) of switches and reconfiguration for restoration is changing the switch status to maximize the supply to loads that are left unsupplied after fault removal. Methods exist for restoration of distribution systems and can be categorized into heuristics, knowledge based, meta-heuristics and intelligent techniques. However, the application of these methods have not considered the unbalanced nature of distribution system operation with mutual coupling. The restoration in this dissertation is achieved using optimization with multiple objectives; that of maximizing the load giving priority to vital loads and minimizing the number of switch operations. Also a restoration scheme for shipboard power systems with an IPS and distributed generation has been developed. Restoration with possible islanding is demonstrated.

A three-stage Experimental Spatial Power Flow (ESPF) method which computes an experimentally derived, spatially continuous representation of the structural power in l-D and 2-D structures is presented. The three stages of the ESPF method consist of first using a scanning laser Doppler vibrometer (SLDV) to acquire spatially dense measurements of the structure's dynamic response. Second, the continuous 3-D complex-valued velocity field is solved from the laser data. Third, a spatially continuous model of the power is computed from the velocity-field model obtained in stage 2. The results of the ESPF method were validated by using both simulated and experimental laser data. In the simulated laser data cases, the power injected into a simply supported plate computed analytically, compared to within 1.33% of the power injected as computed by the ESPF method. In the experimental validation, three methods were used to compute the power injected and extracted from a simply supported plate forced with two shakers. The three methods consisted of the ESPF method and two methods of computing the injected power using impedance head type measurements. The injected power results were compared at four different frequencies. These frequencies were 79.0 Hz, 311.0 Hz, 909.0 Hz, and 1100.0 Hz. In all cases, the injected and extracted power results of the three methods compared to within 20% and to within 12% for all cases except the 909.0 Hz case. These results are currently better than other experimental techniques. Advantages of this method are 1) a spatially continuous representation of the power is computed 2) the affects of the actual boundary conditions and near-field effects of the structure are inherently measured by the SLDV 3) the SLDV does not affect the response of the structure by mass loading and is fully portable for in-field testing 4) the method allows for convergence of the power-flow vector field in addition to convergence of the velocity field and 5) the ESPF method is extendable to account for power due to in-plane motion and to account for shells of arbitrary geometry. / Ph. D.

In the modern power grid, the increasing penetration of intermittent energy sources like solar and wind into the comes with unsought challenges. With increasing smart grid directcurrent (DC) deployments in distribution feeders, microgrids, smart buildings, and highvoltage transmission, there is a need for better understanding the landscape of power flow (PF) solutions as well as for efficient PF solvers with performance guarantees. This thesis puts forth three approaches with complementary strengths towards coping with the PF task, consisting of solving a system on non-linear equations, in DC power systems. We consider a possibly meshed network hosting ZIP loads and constant-voltage/power generators. Uncertainty is another inevitable side-effect of a modern power grid with vast deployments of renewable generation. Since energy storage systems (ESS) can be employed to mitigate the effect of uncertainties, their energy and power ratings along with their charging control strategies become of vital importance for renewable energy producers. This thesis also deals with the task of sizing ESS under a model predictive control (MPC) operation for a single ESS used to smoothen out a random energy signal. To account for correlations in the energy signal and enable charging adjustments in response to real-time fluctuations, we adopt a linear charging policy, designed by minimizing the initial ESS investment plus the average operational cost. Since charging decisions become random, the energy and power limits are posed as chance constraints. The chance constraints are enforced in a distributionally robust fashion. The proposed scheme is contrasted to a charging policy under Gaussian uncertainties and a deterministic formulation. / M.S. / Power systems are undergoing major changes as more renewable energy resources are being deployed across their networks. Two of the major changes are the increase in direct-current (DC) generation and loads and making up for the uncertainty introduced by these resources. In this thesis, we have tackled these two important aspects; a DC power flow (PF) solver and an energy storage system (ESS) sizing under uncertainty. The three DC PF solvers proposed in this thesis exhibit complementary values and can handle a wide range of loads and generation types. We have also proposed a distributionally robust ESS sizing under model predictive control framework, capable of handling worst-case uncertainties.

With the deregulation of power industry and the market competition, reliable power supply and secured system operation are major concerns of the independent system operator (ISO). Power system operation under deregulated environment is very complicated with various possibilities of decisions involved. A robust and fast network analysis tool is one of important functions of conventional EMS, and this function will be reserved for the on-line analysis to deal with varied behaviors of the new deregulated environment. Firstly, a multiple-frequency three-phase load flow model was developed in this dissertation. There are two new sub-models including the fundamental power flow (FPF) and harmonic frequency power flow (HPF) model. In FPF, models of electrical elements and injected power on buses were treated in the form of current injections in a transmission system. The standard Fourier analysis was used to deal with the harmonic loads to get injection currents. With harmonic currents as equivalent current sources, the HPF can be derived. Besides, the fast assumptive model and decoupled model of FPF and HPF, called AFPF, DFPF and DHPF, were also proposed to improve execution time of the load flow programs. Test results show that the proposed general-purpose methods are better performers than conventional power flow solutions and are very robust. Secondly, the novel method, Upstream Tracing Model (UTM) and Downstream Tracing Model (DTM), to trace the power flow in transmission systems based on the converged AC power flow solution was proposed. The method is formulated by using the transmission network structure, the equivalent current-injection and load-admittances from the engineering viewpoint. Four steps are used to trace the linear relationship between each line flow and generator injection power without any assumption and the counter flow can be traced out, then the power consumption on each load can be represented as generators¡¦ contribution. According to the result of tracing, the loss of each line can be allocated to each generator by using a fair line usage concept. This tracing algorithm can calculate each generator¡¦s contribution quickly and fairly, and can be integrated into the existent tariffs of charging for transmission losses and services.

Submitted by Cristina Coutinho de Oliveira null (35131907861) on 2016-04-18T18:23:10Z No. of bitstreams: 1 Defesa_final.pdf: 1997390 bytes, checksum: 8300a03e6985d3d69b82de41b61bb274 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-04-19T15:01:21Z (GMT) No. of bitstreams: 1 oliveira_cc_me_ilha.pdf: 1997390 bytes, checksum: 8300a03e6985d3d69b82de41b61bb274 (MD5) / Made available in DSpace on 2016-04-19T15:01:21Z (GMT). No. of bitstreams: 1 oliveira_cc_me_ilha.pdf: 1997390 bytes, checksum: 8300a03e6985d3d69b82de41b61bb274 (MD5) Previous issue date: 2016-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta proposta apresenta-se um estudo comparativo entre algumas das diversas metodologias existentes na literatura específica para a resolução do Fluxo de Potência (FP) e Fluxo de Potência Continuado (FPC), utilizando métodos baseados em equações de injeção de potência e em equações de injeção de corrente. A formulação de injeção de potência é baseada nas equações de balanço de potência ativa e reativa de cada barra, enquanto que a de injeção de corrente utiliza expressões referentes ao balanço de corrente. É realizada a comparação da influência de três formas de tratamento das barras de geração (PV) nas características de convergência do método de Newton-Raphson simplificado utilizado na solução das equações de fluxo de potência escritas em coordenadas polares, considerando a formulação de injeção de corrente. Também são apresentados os resultados de análises de desempenho entre o método simplificado e o convencional, o qual utiliza as equações de injeção de potência expressa em termos de coordenadas polares. As análises de desempenho são realizadas para os sistemas testes do IEEE de 14, 30, 57, 118 e 300 barras e duas versões reais de grande porte do sistema elétrico SUL/SULDESTE brasileiro 638 e 787 barras considerando: diferentes relações R/X para os ramos e diferentes condições de carregamentos. Os resultados obtidos com duas das formas de tratamento das barras PV mostram que é possível se obter uma melhora nas características de convergência do método simplificado. / This work presents a comparative study on the various existing methods in the literature to solve the power flow (PF) and continuation power flow (CPF), using the methods which are based on power injection equations and current injection equations. The power injection formulation works based on active and reactive power balance equations at each bus, while the current injection using expressions relating to the current balance. In order to make the comparison, the influence of three forms of handling the generation buses (PV) in the convergence characteristics of simplified Newton-Raphson method, used in the solution of the power flow equations in polar coordinates, and by considering the current injection formulation is considered. Moreover, the results of performance tests between the simplified and the conventional methods, which use the power injection equations expressed in terms of polar coordinates, are presented. In order to performance analysis five IEEE test systems such as 14, 30, 57, 118, and 300 bus and two large-scale real electrical power systems such as south Brazilian 638 and 787 bus systems are conducted. The aforementioned systems are tested under different R/X ratios for the branches and different loading conditions. The results show that an improvement in convergence characteristics can be obtained for the simplified method.

Orientador: Dilson Amancio Alves / Resumo: Nesta proposta apresenta-se um estudo comparativo entre algumas das diversas metodologias existentes na literatura específica para a resolução do Fluxo de Potência (FP) e Fluxo de Potência Continuado (FPC), utilizando métodos baseados em equações de injeção de potência e em equações de injeção de corrente. A formulação de injeção de potência é baseada nas equações de balanço de potência ativa e reativa de cada barra, enquanto que a de injeção de corrente utiliza expressões referentes ao balanço de corrente. É realizada a comparação da influência de três formas de tratamento das barras de geração (PV) nas características de convergência do método de Newton-Raphson simplificado utilizado na solução das equações de fluxo de potência escritas em coordenadas polares, considerando a formulação de injeção de corrente. Também são apresentados os resultados de análises de desempenho entre o método simplificado e o convencional, o qual utiliza as equações de injeção de potência expressa em termos de coordenadas polares. As análises de desempenho são realizadas para os sistemas testes do IEEE de 14, 30, 57, 118 e 300 barras e duas versões reais de grande porte do sistema elétrico SUL/SULDESTE brasileiro 638 e 787 barras considerando: diferentes relações R/X para os ramos e diferentes condições de carregamentos. Os resultados obtidos com duas das formas de tratamento das barras PV mostram que é possível se obter uma melhora nas características de convergência do método simplificado. / Abstract: This work presents a comparative study on the various existing methods in the literature to solve the power flow (PF) and continuation power flow (CPF), using the methods which are based on power injection equations and current injection equations. The power injection formulation works based on active and reactive power balance equations at each bus, while the current injection using expressions relating to the current balance. In order to make the comparison, the influence of three forms of handling the generation buses (PV) in the convergence characteristics of simplified Newton-Raphson method, used in the solution of the power flow equations in polar coordinates, and by considering the current injection formulation is considered. Moreover, the results of performance tests between the simplified and the conventional methods, which use the power injection equations expressed in terms of polar coordinates, are presented. In order to performance analysis five IEEE test systems such as 14, 30, 57, 118, and 300 bus and two large-scale real electrical power systems such as south Brazilian 638 and 787 bus systems are conducted. The aforementioned systems are tested under different R/X ratios for the branches and different loading conditions. The results show that an improvement in convergence characteristics can be obtained for the simplified method. / Mestre

abstract: Photovoltaic (PV) power generation has the potential to cause a significant impact on power system reliability since its total installed capacity is projected to increase at a significant rate. PV generation can be described as an intermittent and variable resource because its production is influenced by ever-changing environmental conditions. The study in this dissertation focuses on the influence of PV generation on trans-mission system reliability. This is a concern because PV generation output is integrated into present power systems at various voltage levels and may significantly affect the power flow patterns. This dissertation applies a probabilistic power flow (PPF) algorithm to evaluate the influence of PV generation uncertainty on transmission system perfor-mance. A cumulant-based PPF algorithm suitable for large systems is used. Correlation among adjacent PV resources is considered. Three types of approximation expansions based on cumulants namely Gram-Charlier expansion, Edgeworth expansion and Cor-nish-Fisher expansion are compared, and their properties, advantages and deficiencies are discussed. Additionally, a novel probabilistic model of PV generation is developed to obtain the probability density function (PDF) of the PV generation production based on environmental conditions. Besides, this dissertation proposes a novel PPF algorithm considering the conven-tional generation dispatching operation to balance PV generation uncertainties. It is pru-dent to include generation dispatch in the PPF algorithm since the dispatching strategy compensates for PV generation injections and influences the uncertainty results. Fur-thermore, this dissertation also proposes a probabilistic optimal power dispatching strat-egy which considers uncertainty problems in the economic dispatch and optimizes the expected value of the total cost with the overload probability as a constraint. The proposed PPF algorithm with the three expansions is compared with Monte Carlo simulations (MCS) with results for a 2497-bus representation of the Arizona area of the Western Electricity Coordinating Council (WECC) system. The PDFs of the bus voltages, line flows and slack bus production are computed, and are used to identify the confidence interval, the over limit probability and the expected over limit time of the ob-jective variables. The proposed algorithm is of significant relevance to the operating and planning studies of the transmission systems with PV generation installed. / Dissertation/Thesis / Ph.D. Electrical Engineering 2012

The electric power system is among the biggest and most complex man-made physical network worldwide. The increase of electricity demand, the integration of ICT technologies for the modernization of the electric grid and the introduction of intermittent renewable generation has resulted in further increasing the complexity of operating and planning the grid optimally. For this reason the analysis of large-scale power systems considering all state variables is a very complicated procedure. Thus, it is necessary to explore methods that represent the original network with smaller equivalent networks in order to simplify power system studies. The equivalent network should provide an accurate and efficient estimation of the behavior of the original power system network without considering the full analytical modelling of the grid infrastructure.   This thesis investigates partitioning methods and reduction methodologies in order to develop a proper reduction model. The K-means and K-medoids clustering algorithms are employed to partition the network into numerous clusters of buses. In this thesis the Radial, Equivalent, and Independent (REI) method is further developed, implemented, and evaluated for obtaining a reduced, equivalent circuit of each cluster of the original power system. The basic idea of REI method is to aggregate the power injections of the eliminated buses to two fictitious buses through the zero power balance network.   The method is implemented using Julia language and the PowerModels.jl package. The reduction methodology is evaluated using the IEEE 5-bus, 30-bus, and 118-bus systems, by comparing a series of accuracy and performance indices. Factors examined in the comparison include the chosen number of clusters, different assumptions for the slack bus as well as the effect of the imposed voltage limits on the fictitious REI buses. / Elsystemet är ett av de största och mest komplexa människotillverkade fysiskanätverken i världen. Ökad elförbrukning, integration av informationsteknik föratt modernisera elnäten samt införandet av varierande förnybar elproduktion harresulterat i ytterligare ökad komplexitet för att driva nätet optimalt. Därför ärdet mycket komplicerat att analysera storskaliga elsystem samtidigt som man tarhänsyn till alla tillståndsvariabler. Det är således nödvändigt att utforska metoderför att modellera det ursprungliga nätverket med ett mindre ekvivalent nätverk föratt underlätta studier av elsystem. Det ekvivalenta nätverket ska ge en noggrann ocheffektiv uppskattning av det ursprungliga systemets egenskaper utan att inkludera enkompletta analytisk modell av nätverkets stuktur.Den här rapporten undersöker metoder för att dela upp och reducera ett nätverkför att få fram en lämplig ekvivalent modell. Klusteranalysalgotmerna K-meansoch K-medoids används för att dela in nätverket i ett antal kluster av noder. Irapporten vidareutvecklas, implementeras och utvärderas REI-metoden för att ta framreducerade ekvivalenta nätverk för varje kluster i det ursprungliga systemet. Dengrundläggande idén med REI-metoden är att den aggregerar elproduktionen i deelminerade noderna i två fiktiva noder genom ett nolleffektbalansnätverk.Metoden är implementerad i programspråket Julia och programpaketetPowerModels.jl. Reduceringsmetoderna utvärderas på IEEE:s system med 5 noder,30 noder respektive 118 noder, genom att jämföra ett antal index för noggrannhetoch prestanda. De faktorer som undersäks i jämförelsen inkluderar det valda antaletkluster, olika antagande om slacknoden samt följderna av spänningsgränserna för defiktiva REI-noderna.v

Power flow (PF) control can increase the utilization of the transmission system and connect lower cost generation with load. While PF controllers have demonstrated the ability to realize dynamic PF control for more than 25 years, PF control has been sparsely implemented. This research re-examines PF control in light of the recent development of fractionally-rated PF controllers and the incremental power flow (IPF) control concept. IPF control is the transfer of an incremental quantity of power from a specified source bus to specified destination bus along a specified path without influencing power flows on circuits outside of the path. The objectives of the research are to develop power system operation and planning methods compatible with IPF control, test the technical viability of IPF control, develop transmission planning frameworks leveraging PF and IPF control, develop power system operation and planning tools compatible with PF control, and quantify the impacts of PF and IPF control on multi-decade transmission planning. The results suggest that planning and operation of the power system are feasible with PF controllers and may lead to cost savings. The proposed planning frameworks may incent transmission investment and be compatible with the existing transmission planning process. If the results of the planning tool demonstration scale to the national level, the annual savings in electricity expenditures would be $13 billion per year (2010$). The proposed incremental packetized energy concept may facilitate a reduction in the environmental impact of energy consumption and lead to additional cost savings.

Determining the maximum power system loadability, as well as preventing the system from being operated close to the stability limits is very important in power systems planning and operation. The application of optimization techniques to power systems security and electricity markets is a rather relevant research area in power engineering. The study of optimization models to determine critical operating conditions of a power system to obtain secure power dispatches in an electricity market has gained particular attention. This thesis studies and develops optimization models and techniques to detect or avoid voltage instability points in a power system in the context of a competitive electricity market. A thorough analysis of an optimization model to determine the maximum power loadability points is first presented, demonstrating that a solution of this model corresponds to either Saddle-node Bifurcation (SNB) or Limit-induced Bifurcation (LIB) points of a power flow model. The analysis consists of showing that the transversality conditions that characterize these bifurcations can be derived from the optimality conditions at the solution of the optimization model. The study also includes a numerical comparison between the optimization and a continuation power flow method to show that these techniques converge to the same maximum loading point. It is shown that the optimization method is a very versatile technique to determine the maximum loading point, since it can be readily implemented and solved. Furthermore, this model is very flexible, as it can be reformulated to optimize different system parameters so that the loading margin is maximized. The Optimal Power Flow (OPF) problem with voltage stability (VS) constraints is a highly nonlinear optimization problem which demands robust and efficient solution techniques. Furthermore, the proper formulation of the VS constraints plays a significant role not only from the practical point of view, but also from the market/system perspective. Thus, a novel and practical OPF-based auction model is proposed that includes a VS constraint based on the singular value decomposition (SVD) of the power flow Jacobian. The newly developed model is tested using realistic systems of up to 1211 buses to demonstrate its practical application. The results show that the proposed model better represents power system security in the OPF and yields better market signals. Furthermore, the corresponding solution technique outperforms previous approaches for the same problem. Other solution techniques for this OPF problem are also investigated. One makes use of a cutting planes (CP) technique to handle the VS constraint using a primal-dual Interior-point Method (IPM) scheme. Another tries to reformulate the OPF and VS constraint as a semidefinite programming (SDP) problem, since SDP has proven to work well for certain power system optimization problems; however, it is demonstrated that this technique cannot be used to solve this particular optimization problem.